The present invention relates to a vehicle lamp such as a vehicle tail lamp, a turn signal lamp and a stop lamp, and more particularly to a compact vehicle lamp having inner and outer lenses and a reflector.
There are known vehicle lamps such as tail lamps, turn signal lamps and stop lamps excluding head lamps, which have an inner lens for converting light beams from a light source to parallel light beams. An example of such a conventional vehicle lamp is shown in FIG. 1. This known vehicle lamp comprises a bulb 2 mounted within a housing 1 along an optical axis 0--0, an inner lens 3 and an outer lens 4. The inner lens 3 is a Fresnel cut lens which refracts the light beams from a light emitting point P of the bulb filament and transmits parallel light beams. The outer lens 4 covers the inner lens 3 and has a cutting shape suitable for obtaining a desired divergence property of the transmitted light beams. The focal distance F of the inner lens 3 is generally set at the distance between the inner surface of the inner lens 3 and the light emitting point P of the bulb filament.
The vehicle lamp constructed as above, however, has been found unsatisfactory in the following points. First, since the size, particularly the depth, of the housing 1 of the vehicle lamp is dependent upon the focal distance F of the inner lens 3, if the focal distance F is made short in order to make the vehicle lamp more compact, the incident angle to the inner lens 3 of light beams becomes small, so that the amount of light at the peripheral portion of the inner lens 3 becomes small. Therefore, in practice there is a limit in reducing the size, particularly the depth, of the known vehicle lamp. Second, the vehicle lamp using the inner and outer lenses is less efficient in transmitting the light beams emitted from the bulb when compared to those lamps using a reflector.